WO2007016153A2

WO2007016153A2 - Tilmicosin formulation

Info

Publication number: WO2007016153A2
Application number: PCT/US2006/029000
Authority: WO
Inventors: Paul Reuben Klink; Robin Shane Readnour
Original assignee: Eli Lilly And Company
Priority date: 2005-07-28
Filing date: 2006-07-26
Publication date: 2007-02-08
Also published as: WO2007016153A3

Abstract

The present invention provides an injectable formulation comprising tilmicosin, calcium and a liquid vehicle, methods of using the same, and processes for preparing the same.

Description

TILMICOSIN FORMULATION

BACKGROUND OF THE INVENTION

Tilmicosin is a macrolide antibiotic, 20-dihydro-20-deoxy-20-(cis-3,5- dimethylpiperidin-l-yl)-desmycosin, disclosed in U.S. Pat. No. 4,820,695. Also disclosed in U.S. Pat. No. 4,820,695 are certain injectable, aqueous formulations of tilmicosin. U.S. Pat. No. 5,574,020 discloses certain injectable, aqueous formulations of tilmicosin with the improvement of sustained release. International Patent Application Publication No. WO 2003/034988 discloses certain injectable formulations of tilmicosin and a lipophilic counterion.

Tilmicosin is approved for sale and marketing in the United States for the control of respiratory infection in swine and is limited to oral administration as a medicated feed. Tilmicosin is also approved for sale and marketing in the United States for the treatment and control of respiratory infection in certain ruminant animals. This form is administered by subcutaneous injection and is limited to the treatment of cattle and sheep. Injection of tilmicosin has been shown to be toxic to other animals such as swine and non-human primates and may result in death.

The route of administration is crucial to the tolerance of tilmicosin by the particular animal species. For example, intramuscular injection of tilmicosin in swine is toxic and can cause death at sufficient doses, while intravenous injection of tilmicosin in cattle and sheep is likely to be fatal. Although its modes of administration are limited by these parameters, tilmicosin continues to be valuable to the consuming public. Therefore, a formulation comprising tilmicosin which enhances tolerance by reducing toxicity in tilmicosin-sensitive species (such as swine) is highly desirable.

Humans are also sensitive to tilmicosin and must exercise extreme caution when administering the product to livestock. For example, livestock handlers must use manual syringes to decrease exposure to tilmicosin if an accidental injection does occur. However, such manual syringes are more time consuming and less efficient than automatically powered syringes. Therefore, there is a need for a formulation comprising tilmicosin with enhanced tolerance.

The heart is the principle target of toxicity in certain animals given tilmicosin by oral or parenteral routes. The primary cardiac effects include increased heart rate (tachycardia) and decreased contractility (negative inotropy) which is associated with a decrease in blood pressure. Notably, the significant increase in heart rate and decrease in blood pressure (observed in dogs) following intravenous administration of tilmicosin have been shown to be reversed by subsequent administration of calcium chloride. This suggests that the cardiotoxicity associated with tilmicosin exposure is due in part to antagonism of the calcium channel.

Certain calcium channel antagonists, such as verapamil and dihydropyridine amlodipine, used in the treatment of cardiovascular disorders in humans are known to have cardiovascular-based adverse events when overdosed. These include hypotension and tachycardia. Human overdoses of certain calcium channel blockers have been treated with calcium chloride, calcium gluconate and glucagon, but evidence of a dose response has not been seen, and, as such, these interventions may be regarded as; unproven.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a syringeable injectable tilmicosin formulation comprising tilmicosin, a physiologically acceptable form of calcium and a physiologically acceptable liquid vehicle. More specifically, the present invention provides an injectable tilmicosin formulation comprising 5% to 45% by weight of tilmicosin or a physiological acceptable salt thereof, 0.1% to 25% by weight of calcium, and a physiological acceptable liquid vehicle. The present invention also provides a syringeable injectable tilmicosin formulation useful for the treatment or control of infection in agricultural animals. More specifically, the present invention provides a method of treating infection comprising administering to a domestic animal in need thereof an effective amount of 5% to 45% by weight of tilmicosin or a physiological acceptable salt thereof and 0.1% to 25% by weight of calcium in a physiological acceptable liquid vehicle.

The present invention also provides improved formulations which enhance the tolerance by reduction of toxicity in tilmicosin sensitive animals. More specifically, the present invention provides improved formulations which enhance tolerance in swine.

The present invention also provides a syringeable injectable tilmicosin formulation afforded by: a) combining a calcium salt with a physiological acceptable liquid vehicle and a suitable acid; and b) combining tilmicosin or a physiological acceptable salt thereof with the intermediate of step a.

DETAILED DESCRIPTION OF THE INVENTION Before describing the present invention in greater detail, it is understood that the invention in its broadest sense is not limited to particular embodiments described herein, as variations of the particular embodiments described herein are within the scope of the claimed invention.

The term "injectable" means the ability to administer a liquid solution or suspension by a parenteral route. Parenteral routes of injection include subcutaneous, intramuscular and intravenous with intramuscular being preferred and subcutaneous being more preferred. It is understood the invention may be injected as a depot form or an implant. The term "syringeable" means to adequately pass a liquid solution or suspension through a syringe needle. It will be recognized certain characteristics may influence syringeability such as viscosity of the formulation, temperature, whether a sample is being drawn into or ejected from a syringe, and needle diameter or gauge. As formulations of the present invention will generally be administered in the field under various weather conditions including cold temperature, a formulation which is syringeable without the aid of a warming device is generally preferred. Syringeability may conveniently be assessed by measuring the time usually in seconds to draw a 5 niL to 25 mL volume of sample at a temperature of -10⁰C to 4O⁰C through a needle of 12 to 20 gauge into a 10 mL to 50 mL syringe under a reduced pressure or vacuum of 5 inches to 15 inches Hg. Formulations of the present invention with syringeablilty for a 10 mL sample passing through a 16 or 18 gauge needle under vacuum of 15 inches Hg at room temperature at a value less than 180 seconds are preferred with values less than 60 seconds more preferred. The term "tilmicosin" means 20-dihydro-20-deoxy-20-(cis-3,5-dimethylpiperidin- l-yl)-desmycosin. It is understood that formulations of the present invention contain at least 5% by weight of tilmicosin, but may be varied depending upon the particular form and may conveniently contain up to about 75% by weight of tilmicosin. Formulations of the present invention containing 5% to 45% by weight tilmicosin are preferred with those containing 24% to 36% by weight tilmicosin being more preferred. Formulations of the present invention containing 28% to 32% by weight tilmicosin are even more preferred. The concentration of tilmicosin in tilmicosin technical material may vary. The quantity of tilmicosin technical material is adjusted so that the resulting formulation contains the desired tilmicosin concentration. The term "tilmicosin technical material" refers to an ingredient which contains tilmicosin active ingredient (as defined in the previous paragraph) along with other related substances and/or impurities.

The term "physiologically acceptable salt" refers to an addition salt that exists in conjunction with an acidic or basic portion of tilmicosin. Physiological acceptable salts include the pharmaceutically acceptable salts listed in HANDBOOK OF PHARMACEUTICAL SALTS: PROPERTIES, SELECTION AND USE, P. H. Stahl and C. G. Wermuth (Eds.), Wiley- VCH, New York, 2002 which are known to the skilled artisan. Physiological acceptable salt forms of tilmicosin which are compatible with the components of the formulation particularly the calcium salt form are generally preferred. The skilled artisan will recognize that compatible salt forms of tilmicosin include those which provide a syringeable injectable formulation solution or suspension without adverse physical changes such as undesirable phase separation. Physiological acceptable salt forms of tilmicosin which provide formulation homogeneity are preferred. In the preparation of formulations of the present invention it will be recognized that, in general, the acid addition salts are more aqueous soluble than the free base form of tilmicosin. It will also be recognized that an acid addition salt form of tilmicosin may be formed prior to preparation of the formulation or alternatively formed during the preparation of the formulation by the addition of a suitable acid. In the case where an acid addition salt is formed prior to the preparation of the formulation, it is understood that a percent "by weight tilmicosin" means the weight of tilmicosin in free base form contributed from the weight of the particular tilmicosin acid addition salt. The term "calcium" means divalent cationic calcium, Ca²⁺. It is understood that in the present invention, a convenient source of calcium is in the form of a suitable calcium salt. It is also understood that in determining the percent by weight calcium, the skilled artisan may use known instrumental techniques to assay formulation samples. Alternatively, the percent weight calcium may be calculated on a molar basis from the percent weight calcium salt contribution for a particular formulation. It is understood that formulations of the present invention contain at least 0.1% by weight calcium, but may vary depending upon the particular form and may conveniently contain up to about 50% by weight of calcium. Formulations of the present invention containing 0.1% to 25% by weight of calcium are preferred with those containing 0.1% to 10% by weight being more preferred.

The term "calcium salt" means a calcium ion chemically bound through ionic attractions to a suitable anionic counterion. It is understood that in selecting a suitable calcium salt, the skilled artisan may consider certain properties such as solubility, molecular weight, and physiological compatibility. Physiological compatible calcium salts include the pharmaceutically acceptable calcium salts listed in HANDBOOK OF PHARMACEUΉCAL SALTS: PROPERTIES, SELECTION AND USE, P. H. Stahl and C. G. Wermuth (Eds.), Wiley- VCH, New York, 2002 which are known to the skilled artisan. Calcium salts which are compatible with the components of the formulation including the physiological acceptable salt forms of tilmicosin are generally preferred. The skilled artisan will recognize that compatible calcium salts include those which provide a syringeable injectable formulation solution or suspension without adverse physical changes such as undesirable phase separation. Physiological compatible calcium salts which provide formulation homogeneity are more preferred. Calcium salts include but are not limited to calcium formate, calcium acetate, calcium benzoate, calcium carbonate, calcium propionate, calcium salicylate and calcium lactate with calcium chloride and calcium gluconate being preferred. The term "physiologically acceptable liquid vehicle" means a physiologically acceptable liquid suitable for the preparation of a solution or suspension form of the present invention. In solution form, the liquid vehicle is a solvent optionally containing one or more co-solvents capable of dissolving components of the formulation. Preferred solvents include water with purified water such as deionized water being more preferred. The term co-solvent includes physiologically acceptable water miscible co-solvents such as ethanol, glycerol, propylene glycol, polyethylene glycol and the like.

In a suspension form of the present invention, the physiologically acceptable liquid vehicle is a liquid suspending medium optionally containing one or more adjuvants. The suspending media can be, for example, aqueous polyvinylpyrrolidone, inert oils such as vegetable oils or refined mineral oils, or aqueous carboxycellulose. Suitable physiologically acceptable adjuvants may be required to minimize the likelihood of suspension separation. Suitable adjuvants include thickeners such as gelatin, and surfactants such as organic sulfonates. It will be recognized that formulations of the present invention may optionally contain antibacterial agents, such as benzyl alcohol or methyl paraben; antioxidants, such as vitamin E, vitamin B, ascorbic acid or sodium bisulfite; and chelating agents, such as ethylene diaminetetraacetic acid.

A formulation of the present invention may be made by a process, which is analogous to one known in the art for the production of formulations or by a novel process described herein. Such processes useful for the manufacture of a formulation of the present invention as defined below are provided as further features of the invention and are illustrated by the following procedures. Techniques and reagents for preparation of formulations of the present invention are well known and appreciated in the art (DEVELOPMENT AND FORMULATION OF VETERINARY DOSAGE FORMS, G. E. Hardee and J. D. Baggot (Eds.), Marcel Dekker, Inc. New York 1998).

As used herein, the term "animal" refers to a domestic animal which is infected or at risk of infection of one or more microorganism species. It is understood that within the scope of the meaning of the term domestic animal are livestock including mono-gastric livestock such as swine and ruminant livestock such as cattle, sheep and goats.

The terms "treat," "treatment" and "treating" include all processes wherein there may be an eradication, slowing, interrupting, arresting, controlling, or stopping the progression of the infection described herein and is intended to include prophylactic treatment of the infection.

As used herein, the term "effective amount" refers to an amount, that is, the dosage which is effective in treating or preventing the infection described herein. The attending veterinarian can readily determine an effective amount by the use of conventional techniques and by observing results obtained under analogous circumstances. In determining an effective amount, the dose of a formulation comprising tilmicosin and calcium, a number of factors are considered by the attending diagnostician, including, but not limited to the species of mammal; its size, age, and general health; the specific infecting organism or organisms involved; the degree of involvement or the severity of the infection, the response of the individual animal; the mode of administration; the bioavailability characteristics of the preparation administered; the dose regimen selected; the use of other concomitant medication; and other relevant circumstances. The skilled artisan will recognize tilmicosin possesses an antibiotic spectrum of activity against predominantly gram-positive microorganisms. Tilmicosin also has activity against certain gram-negative and mycoplasma microorganisms. Particular microorganisms which tilmicosin has activity against include Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, Mycoplasma dispar, Mycoplasma bovirhinis and Mycoplasma bovoculi.

An effective amount of the dose of a formulation comprising tilmicosin and calcium is expected to vary from about 1 milligram per kilogram of body weight per day (mg/kg/day) to about 100 mg/kg/day tilmicosin and 0.1 milligram per kilogram of body weight per day (mg/kg/day) to about 50 mg/kg/day calcium. Preferred amounts may be determined by one skilled in the art. EXAMPLES

Example A: Preparations

Preparation 1

To a solution of 40% wt/wt calcium chloride dihydrate in water (10.2 g) is added 37% hydrochloric acid (1.2 g) and glycerol (2.0 g). Tilmicosin technical material (6.6 g) is added and the resulting mixture is stirred to form a solution. A pH of 6.0 is maintained by the addition of 31% hydrochloric acid.

Preparation 2

To purified water (61.3 g) is added 37% hydrochloric acid (12 g) and ethanol (20 g). Tilmicosin (66 g) is added and the resulting mixture is agitated with a dispersator to form a solution. Calcium chloride dihydrate (40.6 g) is added and the resulting mixture is agitated with a dispersator to form a solution. A pH of 7.3 is maintained by the addition of 37% hydrochloric acid.

Preparation 3 To a solution of Preparation 2 (50 g) is added tilmicosin (1.7 g) and ethanol (3.3 g).

Preparation 4

To purified water (41.08 g) is added 37% hydrochloric acid (12.05 g) and ethanol (39.93 g). Tilmicosin (66 g) is added and the resulting mixture is agitated with a dispersator to form a solution. Calcium chloride dihydrate (41.36 g) is added and the resulting mixture is agitated with a dispersator to form a solution. A pH of 7.4 is maintained by the addition of 37% hydrochloric acid.

Preparation 5

To purified water (29.98 g) is added 37% hydrochloric acid (12.00 g) and ethanol (60.00 g). Tilmicosin (65.99 g) is added and the resulting mixture is agitated with a dispersator to form a solution. Calcium chloride dihydrate (31.99 g) is added and the resulting mixture is agitated with a dispersator to form a solution. A pH of 7.3 is maintained by the addition of 37% hydrochloric acid.

Preparation 6 To a solution of 40% wt/wt calcium gluconate monohydrate and 5% wt/wt boric acid in water (22.01 g) is added water (9.98 g) and 37% hydrochloric acid (2.45 g). Tilmicosin (15.5 g) is added and the resulting mixture is stirred to form a solution. A pH of 6.0 is maintained by the addition of 37% hydrochloric acid.

Preparation 7

To a solution of 40% wt/wt calcium gluconate monohydrate and 5% wt/wt boric acid in water (22.11 g) is added purified water (10.06 g), propylene glycol (5.01 g) and 37% hydrochloric acid (2.25 g). Tilmicosin technical material (15.49 g) is added and the resulting mixture is stirred to form a solution.

Example B: Syringeability

A value reflecting syringeability is determined by measurement of the time in seconds to draw a 10 mL sample at a known temperature through a needle of a given gauge into a 20 mL syringe under 15 inches (Hg) of vacuum (Table A).

Table A

Example C: Determination of Tilmicosin Concentration A gradient reversed-phase HPLC system using ultraviolet detection is used to determine the concentration of tilmicosin in a formulation. The HPLC system consists of an injector, pump, degasser and UV detector. A SB-Cl 8 column (3.5 micron, 75 x 4.6 mm LD.) is used to separate sample components. The mobile phase is a linear gradient composition comprising acetonitrile, water and a small amount of trifluoroacetic acid. The flow rate is 1.0 mL/min. The column temperature is determined and the injection volume is 20 μL. The UV detector is set at 295nm and the run time is 15 minutes. The sample is diluted with methanol and water. A standard curve is prepared from determined values for samples containing a known concentration of tilmicosin. The concentration of tilmicosin in the test sample is determined by peak area comparison to the standard curve. Three replicates are determined for each sample. Preparation 3 comprises 299 mg/niL tilmicosin.

Example D: Determination of Calcium Concentration

Inductively Coupled Plasma (ICP) spectrometry is used to determine the concentration of calcium in a formulation. An assay sample is prepared by weighing (in duplicate) 0.1 mL of a formulation (i.e. Preparation 3) into 50 mL of 0.1 N hydrochloric acid. A standard curve is prepared from determined values for samples containing a known concentration of calcium. Check standards are analyzed following calibration standards and sample analysis to determine instrument drift. Preparation 3 comprises 5.65% by weight calcium.

Example E: Tolerance in Tilmicosin Sensitive Animals

Yorkshire X Landrace crossbred barrow pigs (21 to 35 days of age) weighing approximately 16 kg with sound structure and good health are selected. Pigs are conditioned to individual housing, heart monitor connections and protective jackets prior to dosing. Each treatment consists of a single intramuscular (IM) injection in the semitendinosus muscle of either the right or left ham using a 1.5 inch, 18 gauge needle. Pigs are observed for abnormal clinical signs of toxicity such as respiration (rapid respiration, shallow respiration, gasping, panting, vocalization), state of activity (standing normally, ataxia, lethargy, laterally recumbent, dorsally recumbent, restlessness, lameness), and appearance (muscular contractions [i.e., tremors or convulsions], reddening of skin, salivation, vomiting, overall morbidity/mortality and/or any other abnormal clinical signs at each time period that pigs are observed). Moribund animals are euthanized as appropriate.

A single intramuscular injection of Micotil® (tilmicosin phosphate injection, 300 mg/mL, Elanco) at a dose of 25 mg/kg tilmicosin resulted in the development of clinical abnormalities in pigs that are classified as severe. Within 3 hours of administration, 3 of 4 animals died or were euthanized as a result of being moribund. Micotil® does not comprise calcium. A single intramuscular injection of the formulation of Preparation 3 at a dose of 25 mg/kg tilmicosin and 4.7 mg/kg calcium resulted in the development of clinical abnormalities in pigs that are classified as mild. Several days following administration, 0 of 8 animals died or were euthanized as a result of being moribund. The present invention provides improved formulations which enhance the tolerance in tilmicosin-sensitive animals such as pigs by reducing the degree of clinical abnormalities and level of mortality (Table B).

Table B

Claims

We Claim:

1. An injectable tilmicosin formulation comprising: 5% to 45% by weight of tilmicosin or a physiological acceptable salt thereof;

1 to 25% by weight of calcium; and a physiological acceptable liquid vehicle.

2. A formulation of claim 1, comprising: 24% to 36% by weight of tilmicosin or a physiological acceptable salt thereof; and 0.1% to 10% by weight of calcium.

3. A formulation of claim 1 , wherein the physiological acceptable liquid vehicle comprises water and a water miscible co-solvent.

4. An injectable tilmicosin formulation afforded by: a) combining a calcium salt with a physiological acceptable liquid vehicle and a suitable acid; and b) combining tilmicosin or a physiological acceptable salt thereof with the intermediate of step a.

5. A formulation of claim 4, wherein the physiological acceptable liquid vehicle comprises water and a water miscible co-solvent.

6. A method of treating infection comprising administering to a domestic animal in need thereof an effective amount of

5% to 45% by weight of tilmicosin or a physiological acceptable salt thereof and 1 to 25% by weight of calcium in a physiological acceptable liquid vehicle.

7. A method of claim 6, wherein the domestic animal is swine.